1. Field of the Invention
This invention relates to an audio and video recording apparatus using a recording medium such as an optical disk, magnetic disk, magnetic tape or the like and particularly using a re-writable recording medium.
2. Prior Art
Conventional apparatuses for recording audio and video signals on a recording medium use either a magnetic tape or an optical disk as the recording medium. A typical one of those apparatuses using the magnetic tape is a consumer video tape recorder. The consumer video tape recorder first separates a video signal into a luminance signal and a chrominance signal. Then, the luminance signal thus separated is frequencymodulated so that the sync tip is 5.4 MHz and the white peak is 7 MHz. On the other hand, the chrominance signal is subjected to the low band frequency conversion so that a sub-carrier of 3.58 MHz becomes 629 kHz, and amplitudemodulated to become an AM wave having a frequency band of about 1 MHz. In the gap between the FM luminance signal and the AM chrominance signal, an FM audio signal obtained through frequency-modulation of two channel audio signals is inserted to perform a frequency-division multiplex recording.
In addition, a typical example of those apparatuses using the optical disk is the so-called laser disk used only for reproduction which makes the best use of fast accessibility of the optical disk. With the reproduction-only optical disk, the video signal of NTSC is directly frequencymodulated, and the two-channel audio signal is frequencymodulated and frequency-division multiplexed in the low frequency area or the same signal as the audio signal of a compact disk is frequency-division multiplexed in the low frequency area.
Also, as a system proposed first from Britain's IBA for broadcasting via satellite, the Multiplexed Analogue Component (MAC) system is known. See "Video Synchronizing Signal standards and their Trend (No. 6)", Hoso Gijutsu (Broadcasting Technologies), pp. 92-97, April, 1986. As the MAC system, such systems as A-MAC, B-MAC, C-MAC, D-MAC and D2-MAC are known. A common point of these systems is the inline time-division multiplex in which the luminance signal is transmitted every line and two chrominance difference signals are transmitted alternately every line. In addition, the audio signal is a digital signal and subjected to the in-line time-division multiplex with the video signal.
With the consumer video tape recorders and the reproduction-only optical disk players, the video signal and audio signal are subjected to frequency-division multiplex recording, so that either the after-recording or the independent editing of the audio or video signal is impossible.
Also, the consumer video tape recorders using two or more carriers will generate cross modulation. On the other hand, the optical disk players will generate cross color or cross luminance interference.
The MAC system is a system proposed contingent upon broadcasting via satellite originally and the video and audio signals are subjected to the time-division multiplex in each line. Therefore, such problems occur that the time axis compression ratio of each signal becomes high and that when the recording and erasing of the audio or video signal is to be carried out repeatedly, the control becomes difficult due to the eccentricity of the optical disk or uneven rotation of the turn-table.